2004 Atlantic hurricane outlook

Monday, May 24, 2004

WASHINGTON, USA: The National Oceanic and Atmospheric Administration's (NOAA) 2004 Atlantic hurricane season outlook indicates a 50% probability of an above-normal hurricane season, a 40% probability of a near-normal season, and a 10% chance of a below-normal season, according to a consensus of scientists at NOAA’s Climate Prediction Center (CPC), the Hurricane Research Division (HRD), and the National Hurricane Center (NHC).

The outlook calls for 12-15 tropical storms, with 6-8 becoming hurricanes, and 2-4 of these becoming major hurricanes and indicates a likely continuation of above-normal activity that began in 1995.

The predicted 2004 activity is based primarily on the ongoing active phase of the Atlantic multi-decadal signal, but also reflects expected warmer sea surface temperatures (SSTs) in the tropical Atlantic and Caribbean Sea than can be accounted for by the multi-decadal signal alone.

The outlook also reflects the likelihood that conditions (no El Niño or La Niña) will continue through August-October, the peak months of the hurricane season. An updated hurricane outlook will be issued in early August.

Many of the tropical storms and hurricanes in 2004 are likely to form during August-October over the tropical Atlantic and Caribbean Sea. These systems generally track westward toward the United States and Caribbean Sea as they strengthen.

Historically, similar seasons have averaged 2-3 landfalling hurricanes in the continental United States and 1-2 hurricanes in the region around the Caribbean Sea.

However, it is currently not possible to confidently predict at these extended ranges the number or intensity of landfalling hurricanes, or whether a given locality will be impacted by a hurricane this season.

Beginning with 1995 all of the Atlantic hurricane seasons have been above normal, with the exception of the two El Niño years (1997 and 2002). This increased activity contrasts sharply with the generally below-normal activity observed during the previous 25-year period 1970-1994.

The atmospheric and oceanic conditions controlling these very long-period fluctuations in hurricane activity are referred to as the Atlantic multi-decadal signal.

The active phase of the Atlantic multi-decadal signal began in 1995 and has been a primary contributing factor to the increased hurricane activity observed since that time. This signal is a main factor guiding this year’s outlook.

Atlantic hurricane seasons exhibit prolonged periods lasting decades of generally above-normal or below-normal activity. These multi-decadal fluctuations in hurricane activity result nearly entirely from differences in the number of hurricanes and major hurricanes forming from tropical storms first named in the tropical Atlantic and Caribbean Sea.

Tropical cyclone activity during 1995-2003 has been considerably above normal in response to the active phase of the Atlantic multi-decadal signal. During 1995-2003 hurricane seasons have averaged 13 tropical storms, 7.6 hurricanes, and 3.6 major hurricanes.

NOAA classifies all but two of these nine seasons (the El Niño years of 1997 and 2002) as above normal. In contrast, during the preceding 1970-1994 period, hurricane seasons averaged 9 tropical storms, 5 hurricanes, and 1.5 major hurricanes.

CAUTIONARY NOTES

1) It is important to recognize that it is currently not possible to confidently predict at these extended ranges the number or intensity of landfalling hurricanes, or whether a particular locality will be impacted by a hurricane this season. Therefore, residents and government agencies of coastal and near-coastal regions should always maintain hurricane preparedness efforts regardless of the overall seasonal outlook.

2) Far more damage can be done by one major hurricane hitting a heavily populated area than by several hurricanes hitting sparsely populated areas or, of course, not making landfall at all. Therefore, hurricane-spawned disasters can occur even in years with near-normal or below-normal levels of activity. Examples of years with near-normal activity that featured extensive hurricane damage and numerous fatalities include 1960 (Hurricane Donna), 1979 (Hurricanes David and Frederic), and 1985 (Hurricanes Elena, Gloria and Juan). Moreover, the nation's most damaging hurricane, Andrew in 1992, occurred during a season with otherwise below normal activity.

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